Battery pack with protective circuit board and electric bicycle including the battery pack

ABSTRACT

To provide a battery pack that is less likely to be affected by vibrations, shocks and the like and has a stable characteristic, and an electric bicycle that uses the battery pack. 
     A battery pack includes: a battery protective member having a first plate section and a second plate section which is integrally connected to both edge portions of a width direction of the first plate section and extends substantially in a direction perpendicular to both surfaces of the first plate section, wherein the flat batteries are placed on the first plate section; and a protective circuit board. A moistureproof film for the protective circuit board is formed using a plurality of film forming materials different in viscosity, hardness, and thixotropic properties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a battery pack, which is formed byconnecting a plurality of secondary batteries, and an electric bicyclein which the battery pack is installed.

2. Description of Related Art

In electric bicycles, various kinds of secondary batteries are used aspower sources for drive or auxiliary drive. Among the above secondarybatteries, a lithium ion secondary battery, in which charge anddischarge take place as lithium ions move between positive and negativeelectrodes, is preferably used as a battery for a drive power sourcebecause the lithium ion secondary battery has the following batterycharacteristics: high energy density and high output power.

The following lithium ion batteries are known: a lithium ion batterythat is in the shape of a cylinder around which positive and negativeelectrodes are stacked and wound via separators; and a flat lithium ionbattery in which positive and negative electrodes are stacked viaseparators.

Among the above lithium ion batteries, the flat lithium ion battery ispreferably used as a battery for a power source of a device drivingmotor or the like because it is easy to increase capacity per unitbattery by increasing the number of positive and negative electrodesstacked or by increasing the areas of positive and negative electrodes.

As for a unit battery of the flat lithium ion battery, it is possible tomake effective use of the high energy density that the lithium ionbattery has by covering battery elements with a film casing material.

The film-covered battery is used in various ways. For example, what isproposed in Patent Document 1 (JP-A-2007-257901) is a battery pack foran electric bicycle that uses a film-covered battery.

SUMMARY OF THE INVENTION

The following electric bicycles are known: an electric bicycle that isdesigned to reduce burden on a rider when the bicycle is running withthe help of an operation of an attached motor; and an electric bicyclethat can be self-propelled even when a rider is not pedaling. A motor, adriving device, and a motor-driving battery add to the mass of anelectric bicycle. Therefore, such devices are required to be smaller inmass. The electric bicycles require a large-capacity battery whenrunning a long distance or for a long time in order to make use of anoperation of a motor.

Among the various kinds of batteries, a lithium ion battery that islarge in gravimetric energy density and volumetric energy density ispreferably used for an electric bicycle. Among the above batteries, afilm-covered battery, which is covered with a film casing material, ischaracterized by high energy efficiency compared with a battery forwhich a metal can is used as a casing material.

When the electric bicycle is used in rainy conditions, water could getinto the battery pack. Further, water condensation or the like couldoccur inside the battery pack due to temperature change.

Although the battery is covered by a material having high sealingproperties, a protective circuit board used in the battery pack islikely to malfunction or deteriorate due to presence of liquid.

There are mounted, on the protective circuit board, comparativelysmall-sized electronic parts for handling a signal and large-sizedelectronic parts for controlling main current. Conventionally, to coverall these electronic parts with a moistureproof film, a dam memberhaving a height exceeding a height of tall electronic parts is formed,and then a film forming material is poured inside the dam member. Thisinvolves an additional process of forming the dam member and unnecessaryuse of the film forming material.

There is an electric bicycle whose wheel is mounted on a bearing that isattached to the body of the bicycle via a suspension. However, theimpact imposed on the bicycle body is significantly different from thaton an automobile. Therefore, a battery pack attached to the body of thebicycle is greatly affected by shocks and vibrations from a roadsurface, and measures are required to be taken in this regard.

To solve the above problem, according to an aspect of the presentinvention, there is provided a battery pack including: a batteryconnecting structure in which a plurality of flat batteries are placed;and a protective circuit board that protects the flat batteries duringcharging and discharging of the flat batteries, and film formation forthe protective circuit board being made using a plurality of filmforming materials different in viscosity, hardness, and thixotropicproperties.

In the battery pack, film formation for circuit components having alarge length from a surface of the board is made using a film formationmaterial having high before curing viscosity.

In the battery pack, film formation for the circuit components having alarge length from the board surface is made using a film formationmaterial having high viscosity, high hardness, and high thixotropicproperties.

In the battery pack, the battery connecting structure includes a batteryprotective member having a first plate section and a second platesection which is integrally connected to both edge portions of a widthdirection of the first plate section and extends substantially in adirection perpendicular to both surfaces of the first plate section, andthe flat batteries are placed on the first plate section.

In the present invention, “substantially perpendicular” includes asituation where it is effectively possible to obtain perpendicular anddesired operations and effects, for example, including an angle of 80 to100 degrees.

In the battery pack, a surface on which the flat batteries are placed isformed on both surfaces of the first plate section.

In the battery pack, a flat-plate surface of the flat battery is put onthe first plate section.

In the battery pack, the flat batteries are film-covered batteries.

In the battery pack, pull-out tabs of the flat batteries are taken outin the longer direction of the first plate section of the protectivemember.

In the battery pack, one adhesive side of a two-sided adhesive tape isattached to the flat battery, which then adheres to the first platesection or an adjoining flat battery surface.

According to another aspect of the present invention, there is providedan electric bicycle including the above-described battery pack.

Advantages of the Invention

According to the battery pack of the present invention, only applicationof film forming materials having different physical properties allowscomponents mounted on the protective circuit board to be coated with amoistureproof film, thereby ensuring excellent productivity.

Energy-efficient lithium ion batteries or the like covered with the filmcasing material can definitely be protected from shocks and the like bythe lightweight battery protective member of the present invention, sothat even if the battery pack is constantly affected by vibrations andshocks when being used as in a battery pack of an electric bicycle, itis possible to expect that stable operation is maintained for a longtime.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are diagrams showing a unit battery 100 that makes up abattery pack according to an embodiment of the present invention. FIG.1A is a diagram showing the unit battery 100 whose opening is sealedwith heat-sealing sections formed on four sides. FIG. 1B is a diagramshowing the unit battery 100 whose opening is sealed with heat-sealingsections formed on three sides.

FIG. 2 is a diagram showing how to connect a connection tab 125 to apositive-electrode pull-out tab 120 of the unit battery 100.

FIG. 3 is a diagram showing the situation where holes are made on apositive pull-out tab and negative pull-out tab for connecting unitbatteries 100 in series.

FIGS. 4A-4D are diagrams illustrating a holder member 200 that makes upthe battery pack according to the embodiment of the present invention.

FIG. 5 is a perspective view of a board 300 that is used in connectingunit batteries 100 in series in the battery pack according to theembodiment of the present invention.

FIGS. 6A and 6B are diagrams illustrating a battery protective member400 that makes up the battery pack according to the embodiment of thepresent invention.

FIG. 7 is a diagram illustrating a process of producing a batteryconnecting structure 500 that makes up the battery pack according to theembodiment of the present invention.

FIG. 8 is a diagram illustrating a process of producing the batteryconnecting structure 500 that makes up the battery pack according to theembodiment of the present invention.

FIG. 9 is a diagram illustrating a process of producing the batteryconnecting structure 500 that makes up the battery pack according to theembodiment of the present invention.

FIG. 10 is a diagram illustrating a process of producing the batteryconnecting structure 500 that makes up the battery pack according to theembodiment of the present invention.

FIG. 11 is a diagram illustrating a process of producing the batteryconnecting structure 500 that makes up the battery pack according to theembodiment of the present invention.

FIG. 12 is a diagram illustrating a process of producing the batteryconnecting structure 500 that makes up the battery pack according to theembodiment of the present invention.

FIG. 13 is a diagram illustrating a process of producing the batteryconnecting structure 500 that makes up the battery pack according to theembodiment of the present invention.

FIG. 14 is a diagram illustrating a process of producing the batteryconnecting structure 500 that makes up the battery pack according to theembodiment of the present invention.

FIG. 15 is a diagram illustrating a process of producing the batteryconnecting structure 500 that makes up the battery pack according to theembodiment of the present invention.

FIGS. 16A and 16B are diagrams illustrating a process of producing thebattery connecting structure 500 that makes up the battery packaccording to the embodiment of the present invention.

FIG. 17 is a diagram illustrating a process of producing the batteryconnecting structure 500 that makes up the battery pack according to theembodiment of the present invention.

FIG. 18 is a diagram illustrating a process of producing a battery packaccording to the embodiment of the present invention.

FIG. 19 is a diagram illustrating a process of producing the batterypack according to the embodiment of the present invention.

FIG. 20 is a diagram illustrating a process of producing the batterypack according to the embodiment of the present invention.

FIG. 21 is a diagram illustrating a process of producing the batterypack according to the embodiment of the present invention.

FIG. 22 is a diagram illustrating a process of producing the batterypack according to the embodiment of the present invention.

FIG. 23 is a diagram illustrating a process of producing the batterypack according to the embodiment of the present invention.

FIG. 24 is a diagram illustrating a process of producing the batterypack according to the embodiment of the present invention.

FIG. 25 is a diagram illustrating a process of producing the batterypack according to the embodiment of the present invention.

FIG. 26 is a diagram illustrating an electric bicycle according to theembodiment of the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following describes an embodiment of the present invention withreference to the accompanying drawings. FIG. 1 is a diagram showing aunit battery 100 that makes up a battery pack according to an embodimentof the present invention. What is used for the unit battery 100 is alithium ion secondary battery in which charge and discharge take placeas lithium ions move between positive and negative electrodes.

The unit battery 100 of the present invention has a flat shape andtherefore is also referred to as a flat battery.

A main unit 110 of the unit battery has a structure in which thefollowing components are stored in a film casing material, which is inthe shape of a rectangle in planar view: a laminated electrode assembly,in which a plurality of sheet positive electrodes and a plurality ofsheet negative electrodes are stacked via separators, and anelectrolytic solution (both not shown). From an upper end portion 111 ofthe unit battery main unit 110, a positive-electrode pull-out tab 120and a negative-electrode pull-out tab 130 are pulled out.

The positive-electrode pull-out tab 120 and the negative-electrodepull-out tab 130 are both in the shape of a plate, and are eachconnected directly, or via a lead body or the like, to the sheetpositive electrodes and the sheet negative electrodes in the film casingmaterial. The film casing material includes a heat-sealing resin layeron a plane facing the inside of the battery. Moreover, a film casingmaterial is used for a plane facing the outside of the battery: the filmcasing material is made by stacking protective films on laminatedmetallic foil made of aluminum foil or the like.

More specifically, on a plane that is positioned on the outer-surfaceside of the aluminum foil, a member that has strength and heatresistance, such as nylon or polyethylene terephthalate, is stacked; onthe inner-surface side, a material that is excellent in heat-sealingperformance, such as polypropylene or polyethylene, is stacked.

With a battery element, in which positive and negative electrodes arestacked via separators, and an electrolytic solution stored in the filmcasing material, the periphery of the film casing material, i.e. theupper end portion 111, lower end portion 112 and two side end portions113, is heat-sealed. Therefore, the inside thereof is hermeticallysealed.

In the above unit battery 100, aluminum or aluminum alloy is used as amaterial of the positive-electrode pull-out tab 120; nickel,nickel-plated copper, or nickel-copper clad is generally used as amaterial of the negative-electrode pull-out tab 130. According to thepresent embodiment, the positive-electrode pull-out tab 120 made ofaluminum and the negative-electrode pull-out tab 130 made of nickel areused.

In order to make the battery pack of the present invention, a positivepull-out tab of a unit battery 100 and a negative pull-out tab of a unitbattery 100, which is adjacent to the above unit battery 100, aremechanically bound together with bolts and nuts and therefore connectedtogether electrically. In this case, the structure in which the aluminumpositive-electrode pull-out tab 120 of the unit battery 100 and thenickel negative-electrode pull-out tab are mechanically bound togethercould lead to a decline in conductivity after a predetermined period oftime has passed due to problems pertaining to differences in potential.Accordingly, in the battery pack of the present invention, at a pointwhere a positive pull-out tab of a unit battery 100 and a negativepull-out tab, which is adjacent to the above unit battery 100, aremechanically bound together, the pull-out tabs are connected in such away that the members made of nickel come in contact with each other.

The configuration to achieve the above will be described. As shown inFIG. 1, in a process of making the battery pack, suppose that thealuminum positive-electrode pull-out tab 120 of the unit battery 100 hasa length of a from the upper end portion 111, and the nickelnegative-electrode pull-out tab 130 a length of b (b>a) from the upperend portion 111. Then, to the aluminum positive-electrode pull-out tab120 having a length of a, a tab member 125 made of nickel is connectedand added by means of ultrasonic waves so that the length from the upperend portion 111 comes to b (see FIGS. 2 and 3). In order to allow unitbatteries 100 to be connected in series, a hole 127 is made on the tabmember 125, which serves as a positive pull-out tab; a hole 137 is madeon the negative-electrode pull-out tab 130. Incidentally, hereinafter,the entire pull-out tab, which is formed by connecting the tab member125, is also referred to as a positive-electrode pull-out tab 120.

As described below, in the battery pack of the present invention, in aprocess of electrically connecting a plurality of unit batteries 100,the pull-out tabs having different polarities are connected together insuch a way that the nickel members (the tab members 125 and thenegative-electrode pull-out tabs 130) come in contact with each other.Accordingly, the electrically connected portions of the adjoining unitbatteries turn out to be the portions that are made of the same type ofmetallic material and are connected electrically. Therefore, theproblems pertaining to differences in potential do not arise, and it issubstantially possible to prevent a decline over time in conductivityfrom occurring.

The following describes a holder member 200, which is used inelectrically connecting the positive pull-out tabs and negative pull-outtabs of a plurality of unit batteries 100 in the battery pack of theembodiment of the present invention. FIG. 4 is a diagram illustratingthe holder member 200. FIG. 4A is a diagram showing the holder member200 seen from a first main surface side. FIG. 4B is a diagram showingthe holder member 200 seen from a second main surface side. FIG. 4C is across-sectional view of FIG. 4A taken along X-X′. FIG. 4D is a side viewof the holder member 200.

On the holder member 200, a first surface 210 and a second surface 250,which is on the opposite side of the holder member 200 from the firstsurface 210, are formed; the holder member 200 is a member made ofsynthetic resin such as ABS resin. In a first row 211 of the firstsurface 210 of the holder member 200, pull-out tab insertion holes 215are formed side by side from top to bottom as shown in FIG. 4A.Similarly, in a second row 212 of the first surface 210, pull-out tabinsertion holes 215 are formed side by side from top to bottom. When aunit battery 100 is attached to the holder member 200, the pull-out tabinsertion holes 215 provided on the first surface 210 are used. Thepull-out tab insertion holes 215 are holes passing therethrough from thefirst surface 210 to the second surface 250; and holes into which thepull-out tabs of the unit battery 100 can be inserted.

As shown in FIG. 4A, on the upper and lower sides of the first andsecond rows 211 and 212, pull-out tab guide ribs 203 are provided. Apull-out tab guidance section 213 is provided in such a way that thepull-out tab guidance section 213 is sandwiched between the pull-out tabguide ribs 203 of the first row 211. Moreover, a pull-out tab guidanceconcave section 214 is provided in such a way that the pull-out tabguidance concave section 214 is sandwiched between the pull-out tabguide ribs 203 of the second row 212.

In the first row 211, based on regulations by the pull-out tab guideribs 203, a pull-out tab of an edge-side unit battery 100, out of aplurality of unit batteries 100 connected in series, is guided to thesecond surface 250 from the first surface 210 via the pull-out tabguidance section 213.

In the second row 212, based on regulations by the pull-out tab guideribs 203, a pull-out tab of an edge-side unit battery 100, out of aplurality of unit batteries 100 connected in series, is guided to thesecond surface 250 from the first surface 210 via the pull-out tabguidance concave section 214.

Among a plurality of unit batteries 100 connected in series, a pull-outtab of a unit batter 100 that is not on the edge side passes through thepull-out tab insertion hole 215 and is attached to the holder member200. In the upper and lower areas of the pull-out tab insertion hole 215(as shown in FIG. 4A), pull-out tab guide projecting sections 220 areprovided in such a way that the pull-out tab insertion hole 215 issandwiched between the pull-out tab guide projecting sections 220, whichare positioned on the upper and lower sides of the pull-out tabinsertion hole 215. The pull-out tab guide projecting sections 220 aregenerally made up of a top section 221 and two tapered sides 222, whichare seamlessly connected to the top section 221. When a pull-out tab ofa unit battery 100 is inserted into a pull-out tab insertion hole 215, aspace between the two tapered sides 222 becomes gradually narrower,making it easy to attach the unit battery 100 to the holder member 200.Therefore, it is possible to improve efficiency in connecting aplurality of unit batteries 100 in series and increase productivity.

To the second surface 250 of the holder member 200, a board 300 can beattached. On the board 300, the pull-out tabs of the adjacent unitbatteries 100 are bent, put on each other and connected, resulting in anelectrical connection. When the pull-out tabs of the adjacent unitbatteries 100 are connected, the pull-out tabs are mechanically boundtogether with bolts and nuts. Accordingly, six nut housing sections 255for housing nuts 256 are provided in the first row 211 of the secondsurface 250, and five in the second row 212. Moreover, on the secondsurface 250, divider pieces 260, which are designed to ensure insulationbetween the pull-out tab connection sections of a unit battery 100 thatare formed on the board 300 or between pull-out tab connection sectionsand pull-out tabs, are provided at three locations in the first row 211and at two locations in the second row 212.

Positioning projecting sections 263 are projections that help positionthe board 300 when the board 300 is attached to the holder member 200;one positioning projection section 263 is positioned in the first row211, and the other in the second row 212. Moreover, one screw hole 270,which is used to bind the board 300 and the holder member 200 togetherafter the board 300 is attached to the holder member 200 with the use ofthe above positioning projecting sections 263, is provided in the firstrow 211, and the other in the second row 212.

The following describes the configuration of the board 300 on whichconnection sections for the pull-out tabs of a plurality of unitbatteries 100 are formed in the battery pack of the embodiment of thepresent invention.

FIG. 5 is a perspective view of the board 300 that is used in connectingunit batteries 100 in series in the battery pack of the embodiment ofthe present invention.

The board 300, which is made by mainly using glass epoxy or the like asbase material, is attached to the second surface 250 of the holdermember 200 before being used. The peripheral shape of the board 300substantially matches the peripheral shape of the second surface 250 ofthe holder member 200. At two locations on the periphery of the board300, pull-out tab guidance notch sections 314 are formed so as tocorrespond to the pull-out tab guidance concave sections 214 of theholder member 200.

Moreover, on the board 300, pull-out tab extraction holes 315 areprovided so as to correspond to the pull-out tab insertion holes 215 ofthe holder member 200. Moreover, on the board 300, divider pieceextraction holes 317 are provided so as to correspond to the dividerpieces 260 of the holder member 200. Furthermore, on the board 300,pull-out tab/divider piece extraction holes 316 are provided to supportboth the pull-out tab insertion holes 215 and divider pieces 260 of theholder member 200. The above holes are all through-holes that passthrough the board 300 from one main surface to the other main surface;and are so formed that the pull-out tabs of unit batteries 100, thedivider pieces 260 and the like can be inserted therein.

In areas where the pull-out tabs of unit batteries 100 are fixed to theboard 300 with bolts and nuts, the following sections are provided:thin-film electrode sections 320 a, 320 b and 320 c.

There is an electrical connection between a thin-film electrode sections320 a and a metallic positive terminal electrode washer 321, which isfixed to the board 300. There is an electrical connection between athin-film electrode section 320 c and a metallic negative terminalelectrode washer 322, which is fixed to the board 300. To the positiveterminal electrode washer 321 and the negative terminal electrode washer322, the pull-out tabs of an edge portion of a unit battery 100 that isconnected in series are connected. Therefore, the positive terminalelectrode washer 321 and the negative terminal electrode washer 322 areused as terminals for charge and discharge of power for the batterypack.

Moreover, there is an electrical connection between a thin-filmelectrode section 320 b and a terminal section, not shown, of aconnector 340, allowing the potential for monitoring each unit battery100 to be measured through the connector 340. Incidentally, theconnector 340 may be formed so that a signal from a temperaturemeasurement sensor (not shown) that measures temperatures of unitbatteries 100 can be taken out.

For each of the thin-film electrode sections 320 a, 320 b and 320 c,pull-out tab connection screw holes 325 are provided: pull-out tabconnection bolts 257, which are used to fix the pull-out tabs of unitbatteries 100, are inserted into the pull-out tab connection screw holes325. To the thin-film electrode section 320 a and the thin-filmelectrode section 320 c, one pull-out tab of an edge-portion unitbattery 100, out of the unit batteries 100 connected in series, isfixed. Meanwhile, two thin-film electrode sections 320 b are fixed insuch a way that the pull-out tabs of the adjoining unit batteries 100are bent and put on each other.

On the board 300, two positioning holes 328 are formed so as tocorrespond to the positioning projecting sections 263 provided on thesecond surface 250 of the holder member 200. As the two positioningprojecting sections 263 pass through the positioning holes 328, theholder member 200 and the board 300 can be easily positioned when beingbound together, contributing to an improvement in productivity.Moreover, board fixing screw holes 329, which are formed on the board300, are holes into which board fixing screws 271, which are used to fixthe holder member 200 to the board 300, are inserted.

The following describes a battery protective member 400, which protectsa plurality of unit batteries 100 at a time when the unit batteries 100are connected in series and turned into a battery connecting structure500 in the battery pack of the embodiment of the present invention.

FIG. 6 is a diagram illustrating the battery protective member 400,which makes up the battery pack of the embodiment of the presentinvention. FIG. 6A is a diagram showing the battery protective member400 in a way that faces a first plate section 410 to which a mainsurface of a unit battery 100 is bonded. FIG. 6B is a diagram showingthe battery protective member 400 seen from an upper end of FIG. 6A.

When unit batteries 100 are placed, the battery protective member 400 ofthe present invention is inserted between the unit batteries 100 placedbefore being used.

The battery protective member 400 may be made of synthetic resin, suchas ABS resin, polyethylene terephthalate resin or polycarbonate resin.The use of such a material enables a lightweight and inexpensive batteryprotective member 400 to be realized.

Moreover, the battery protective member 400 may also be made of ametallic member and a member made of synthetic resin with dispersed,highly heat-conductive material particles. The use of such a materialenables a highly heat-conductive and lightweight battery protectivemember 400 to be realized.

More specifically, the metallic member is aluminum, aluminum alloy, orcopper. The highly heat-conductive material particles are aluminumnitride, silicon nitride or alumina.

For the synthetic resin material, the following can be listed: ABSresin, polyethylene terephthalate resin, or polycarbonate resin. Amaterial with highly heat-conductive material particles dispersed in theabove resin can be listed.

Among the above substances, aluminum or aluminum alloy is suitable.

In the case of aluminum, aluminum alloy or the like, an alumitetreatment film or insulating film is preferably formed on the surface.The above film prevents troubles from occurring even when a voltageapplying section comes in contact with the protective member.

The first plate section 410 of the battery protective member 400 is amember that is sandwiched between a unit battery 100 and a unit battery100 that is connected in series to the above unit battery 100.Meanwhile, second plate sections 440 are so provided as to extend in adirection perpendicular to the first plate section 410 from both edgeportions of the first plate section 410. Therefore, as shown in FIG. 6B,the cross-sectional surface of the battery protective member 400 is inthe shape of “H.”

Moreover, a notch section 420, which are made up of the following, isformed on the first plate section 410: a first notch section 421, whichis the deepest notch section; second notch sections 422, which aredisposed on both sides of the first notch section 421 and are the seconddeepest notch sections after the first notch section 421; and thirdnotch sections 423, which are disposed on both sides of the second notchsections 422 and are the shallowest notch sections.

The following describes processes of producing, from each of the abovemembers, a battery connecting structure 500 in which unit batteries 100are connected, with reference to FIGS. 7 to 17. FIGS. 7 to 17 arediagrams illustrating the processes of producing the battery connectingstructure 500, which makes up the battery pack of the embodiment of thepresent invention.

First, in a process shown in FIG. 7, nuts 256 are mounted in all the nuthousing sections 255, which are provided on the second surface 250 ofthe holder member 200. The dimensions of the inner periphery of the nuthousing sections 255 are so set that the nuts 256 cannot be easilyremoved once the nuts 256 are placed into the nut housing sections 255.

In a subsequent process shown in FIG. 8, the positioning projectingsections 263 of the holder member 200 are inserted into the positioningholes 328 of the board 300 so that the holder member 200 and the board300 are positioned. Subsequently, two board fixing screws 271 areinserted into the board fixing screw holes 329 and screwed into screwholes 270. As a result, the holder member 200 is fixed to the board 300.Incidentally, for the board fixing screw holes 329, various kinds ofscrew can be used. However, the use of self-tapping screws helps improvework efficiency during the production process.

In a subsequent process shown in FIG. 9, a unit battery 100 is disposedon the first surface 210 of the holder member 200. Thenegative-electrode pull-out tab 130 of the unit battery 100 is bent soas to come in contact with the thin-film electrode section 320 b of theboard 300 with the help of the pull-out tab guidance concave section214. Moreover, the positive-electrode pull-out tab 120 of the unitbattery 100 is bent so as to come in contact with the thin-filmelectrode section 320 a of the board 300 with the help of the pull-outtab guidance section 213. The pull-out tab connection bolts 257 areinserted into the holes 127 of the positive-electrode pull-out tab 120and the pull-out tab connection screw holes 325; the pull-out tabconnection bolts 257 are screwed into the nuts 256 housed in the nuthousing sections 255. In this manner, the process of mounting the firstunit battery 100 is completed.

A subsequent process shown in FIG. 10 takes place on the first surface210 of the holder member 200. In the process, as shown in the diagram,two strips of two-sided adhesive tape 460 are attached to an upper mainsurface of the unit battery 100. The two-sided adhesive tapes 460 areused to fix the first unit battery 100, which is attached to the holdermember 200, to a second unit battery 100, which is to be attached to theholder member 200. The reason the two strips of two-sided adhesive tape460 are provided on the main surface of the unit battery 100 as shown inthe diagram is to allow a spacer, described later, to be disposedbetween the two strips of two-sided adhesive tape 460 in order toimprove productivity.

In a subsequent process shown in FIG. 11, a spacer (not shown) that isthicker than the two-sided adhesive tapes 460 is placed on the firstunit battery 100 attached. Furthermore, two pull-out tabs of the secondunit battery 100 slide on the spacer and are inserted into the pull-outtab insertion holes 215. As described above, the pull-out tab guideprojecting sections 220 are disposed on the upper and lower sides of thetwo pull-out tab insertion holes 215. Furthermore, the tapered sides 222are provided on the pull-out tab guide projecting sections 220.Therefore, a space between the upper and lower pull-out tab guideprojecting sections 220 becomes gradually narrower, enabling thepull-out tabs of a unit battery to be easily guided to the pull-out tabinsertion holes 215 of the holder member 200.

In this case, the positive-electrode pull-out tab 120 of the first unitbattery 100 attached to the holder member 200 is disposed in the firstrow 211, and the negative-electrode pull-out tab 130 in the second row212. On the other hand, the positive-electrode pull-out tab 120 of thesecond unit battery 100 attached to the holder member 200 is disposed inthe second row 212, and the negative-electrode pull-out tab 130 in thefirst row 211. Hereinafter, in a process of sequentially placing unitbatteries 100, the positive-electrode pull-out tabs 120 of the odd unitbatteries 100 attached are disposed in the first row 211, and thenegative-electrode pull-out tabs 130 in the second row 212. Thepositive-electrode pull-out tabs 120 of the even unit batteries 100attached are disposed in the second row 212, and the negative-electrodepull-out tabs 130 in the first row 211. In this manner, in a directionin which the unit batteries 100 are placed or stacked, the unitbatteries 100 are so disposed that the pull-out tabs of the adjacentunit batteries 100 face different directions. Accordingly, on the board300, connection does not have to take place diagonally with respect tothe placing or stacking direction.

After it is confirmed that the upper end portion 111 of the second unitbattery 100 is pushed into until the upper end portion 111 hits thefirst surface 210 of the holder member 200, a subsequent task starts onthe board 300.

In a subsequent process shown in FIG. 12, the positive-electrodepull-out tab 120 of the second unit battery 100 attached is bentdownward as shown in the diagram, and is put on the negative electrode130 of the first unit battery 100 attached. After that, a pull-out tabconnection bolt 257 is inserted into a hole of each pull-out tab, orpull-out tab connection screw hole 325, and is screwed into a nut 256,forming a connection portion for the negative-electrode pull-out tab 130of the first unit battery 100 attached on the thin-film electrodesection 320 b and the positive-electrode pull-out tab 120 of the secondunit battery 100 attached. In this manner, an electrical connection iscompleted.

Meanwhile, the negative-electrode pull-out tab 130 of the second unitbattery 100 attached is bent upward as shown in the diagram, therebymaking preparations for the positive-electrode pull-out tab 120 of thethird unit battery 100 attached to be connected.

In a subsequent process shown in FIG. 13, in a similar way to the casewhere the second unit battery 100 is attached, a battery protectivemember 400 is attached with the use of a spacer. The upper surface ofthe second unit battery 100 and the lower surface of the batteryprotective member 400 are bonded together with two strips of two-sidedadhesive tape 460. Furthermore, as shown in the diagram, two strips oftwo-sided adhesive tape 460 are attached to the upper surface of thebattery protective member 400. With the use of the two-sided adhesivetapes 460, the battery protective member 400 is fixed to the third unitbattery 100 attached to the holder member 200.

FIG. 14 shows the situation where the third to eighth unit batteries 100are sequentially attached to the holder member 200 and the board 300 ina similar way to that described above. On the board 300, each time oneunit battery 100 is attached, the pull-out tabs are bent and put on eachother, and the pull-out tabs of the adjacent unit batteries 100 areconnected by means of the pull-out tab connection bolts 257. In thismanner, an electrical connection is realized.

In a subsequent process shown in FIG. 15, what is shown is the situationwhere, after the eighth unit battery 100 is attached, still anotherbattery protective member 400 is attached. In this manner, in thebattery connecting structure 500 of the present embodiment, two batteryprotective members 400 are disposed so as to form two battery protectivemember blocks 450, which are protected by the battery protectivemembers. In this manner, each unit battery 100 is protected againstexternal shocks and the like.

Moreover, the unit batteries 100 are so placed as to rise above an upperend portion of a direction of the height between the first plate section420 and the second plate section 440. In this manner, since the unitbatteries are so placed as to rise above the upper end portion of thesecond plate section 440, there is an improvement in heat-releaseperformance from the peripheries of the unit batteries.

Batteries that are placed so as to rise above the upper end portion ofthe above second plate section may be placed on an upper or lowerbattery protective member 400, or both, in the case of the diagram.

FIG. 16 shows the situation where, on the first plate section 420 of thebattery protective member 400, the ninth and tenth unit batteries 100are further attached to the holder member 200 and the board 300.

The negative-electrode pull-out tab 130 of the tenth unit battery 100 isfixed to a thin-film electrode section (not shown) of the board 300 withthe use of the pull-out tab guidance section 213. As a result, thepull-out tabs of the first to tenth unit batteries 100 are eachconnected on the board 300, and a process of connecting ten unitbatteries 100 in series is completed. In this manner, the batteryconnecting structure 500 including two battery protective member blocks450 is completed.

Moreover, in the battery connecting structure 500 shown in the diagram,the unit batteries 100 are so placed as to rise above the upper endportion, in the direction of the height from a surface of the firstplate section 420, of the second plate section 440 of a side of abattery protective member. The sides of some of the unit batteries arenot covered with the second plate section 440[400→440].

Therefore, the air in the surrounding area flows into the unit batteries100 from a space between the second plate sections 440 of the upper andlower battery protective members 400, contributing to an improvement inheat-release performance of the unit batteries 100.

A unit battery 100 covered with a film casing material has aheat-sealing section on the periphery. A side edge portion 113 is notbent; the side edge portion 113 is so large in size that the side edgeportion 113 comes in contact with an inner surface of the second platesection 440 of the battery protective member 400. Therefore, the unitbattery 100 can be precisely positioned on the battery protective member400 and smoothly placed on the first plate section.

The film casing material is flexible. However, on the heat-sealingsection, there is a portion that is higher in rigidity than otherportions. Therefore, the heat-sealing section can sufficiently resist aforce applied from the side edge portion 113, and therefore canwithstand vibrations, shocks and other forces.

FIG. 17 is a diagram showing the battery connecting structure shown inFIG. 16 when seen from the board.

The battery connecting structure includes two battery protective memberblocks 450. A process of charging and discharging ten unit batteries 100connected in series takes place with the use of the positive terminalelectrode washer 321 and negative terminal electrode washer 322 attachedto the board 300. A terminal member 331 is attached to the positiveterminal electrode washer 321, and a terminal member 332 to the negativeterminal electrode washer 322.

As described above, the battery pack of the present invention is made inthe following manner: the positive and negative pull-out tabs of aplurality of unit batteries 100 are inserted into the pull-out tabinsertion holes 215 of the holder member 200, and the pull-out tabshaving different polarities of a plurality of the unit batteries 100 areconnected together on the board 300. Therefore, the production ofbattery packs is highly efficient, resulting in an improvement inproductivity.

Moreover, the pull-out tabs having different polarities of a pluralityof the unit batteries 100 are connected together on the board 300 withpull-out tab connection bolts 257 and nuts 256. Therefore, it is easy toconnect a plurality of unit batteries 100 electrically. Thus, theproduction of battery packs is highly efficient, resulting in animprovement in productivity.

The following describes processes of making a battery pack of thepresent invention using the battery connecting structure 500, which isformed as described above, with reference to FIGS. 18 to 25.

In a process shown in FIG. 18, to a first case body 600 that houses thebattery connecting structure 500, a discharge terminal 613 and a chargeterminal 614 are fixed with screws with the help of a discharge terminalattachment concave section 611 and a charge terminal attachment concavesection 612, which are provided on the first case body 600.

In a process shown in FIG. 19, a first cushioning member 621 is attachedto a second housing section 602 of the first case body 600 with anadhesive or the like, and a second cushioning member 622 to a circuithousing section 603.

In the battery pack of the present invention, as shown in FIGS. 18 and19, a drain hole 682 is provided on a bottom portion of the batterypack, and a drain hole 681 on an upper compartment section 680.

The battery pack is used outdoors. Therefore, rainwater or the likecould get into the battery pack. Water condensation or the like couldoccur as unit batteries and protective circuit board sections in thebattery pack heat up and cool down after the liquid gets in from theoutside.

According to the present invention, in addition to the drain hole 682 onthe bottom portion, another drain hole is provided on the uppercompartment section 680, a compartment in which a protective circuitboard, which could be affected by the liquid, is installed, wherebyliquid can be quickly discharged from inside of the battery pack.Therefore, it is possible to prevent an adverse effect associated withthe liquid.

In a process shown in FIG. 20, to a second housing section 662 of asecond case body 660, a third cushioning member 663 is attached with anadhesive or the like.

In processes shown in FIGS. 21 and 22, to the battery connectingstructure 500, cushioning materials are attached. In the battery pack ofthe present invention, two structures, i.e. a first battery connectingstructure 500 and a second battery connecting structure 500, are storedin the battery pack.

In a process shown in FIG. 21, as for the first battery connectingstructure 500, fourth cushioning members 504, which are thick, areattached to an edge-portion unit battery 100; to the second platesections of all the battery protective members, fifth cushioning members505, which are thinner than the fourth cushioning members 504, areattached. An adhesive or the like is used in attaching the fourthcushioning members 504 and the fifth cushioning members 505 to parts.

Meanwhile, in a process shown in FIG. 22, as for the second batteryconnecting structure 500, fourth cushioning members 504 are attached toan edge-portion unit batter 100; only to the second plate sections of aone-side battery protective member, fifth cushioning members 505 areattached. As in the case described above, an adhesive or the like isused in attaching the fourth cushioning members 504 and the fifthcushioning members 505 to parts.

In a process shown in FIG. 23, a discharge terminal 613, a chargeterminal 614 and a protective circuit board 700 are connected withwires. Moreover, the protective circuit board 700 is fixed to thecircuit housing section 603 of the first case body 600 with screws.

In a process shown in FIG. 24, the first battery connecting structure500A is stored in the first housing section 601 of the first case body600, and the second battery connecting structure 500B in the secondhousing section 602.

In the protective circuit board 700, for tall circuit components such asFETs, a coating material having high viscosity, high hardness, and highthixotropic properties and thus not running down on a surface of theprotective circuit board but forming a film having a predeterminedthickness is used.

On the other hand, for short circuit components, a coating materialhaving low viscosity, low hardness, and low thixotropy is used to form afilm.

As the coating materials for both tall and short circuit components, asilicone-based adhesive material can be used. The use of thesilicone-based material as the coating materials for both tall and shortcircuit components allows formation of a film having a tight interfacebetween the materials having different physical properties. For example,for the tall circuit components, Cemedine SX720W (viscosity: 45 Pa·s 23°C.) consisting primarily of acrylic modified silicone resin can be used;for the short circuit components, SINWE 500 (viscosity: 0.6 Pa·s 25° C.)made by Hong Kong Xinwei Chemical Co., Ltd can be used.

In the protective circuit board 700 of the present invention, of all theportions on the circuit board for which coating is necessary, curableresin having high before curing viscosity may be used to coat a portionat which the tall circuit components such as FETs and curable resinhaving low before curing viscosity may be used to coat the remainingportion. This can reduce unnecessary use of the film forming materialpositioned at a portion for which the coating is unnecessary. Theportion at which the curable resin having high before curing viscosityis used may be set to a portion including the tallest circuit componenton the circuit board surface.

The curable resin to be used for the protective circuit board 700 to beused, particularly, in the electric bicycle, is preferably asilicone-based adhesive material that reacts with two types of waterhaving before curing viscosities at room temperature (e.g., about 25°C.) of 20 Pa·s to 90 Pa·s and 0.3 Pa·s to 1.0 Pa·s, respectively tocure. The use of such an adhesive material allows the circuit board tobe used in the protective circuit board 700 of the battery pack forelectric bicycle to be coated satisfactorily.

The first battery connecting structure 500A, to which cushioning membershave been attached, is stored in the first housing section 601 in such away that a direction CP in which clearance is positive is parallel tothe bottom face of the first housing section 601, and a direction CM inwhich clearance is negative is perpendicular to the bottom face of thefirst housing section 601.

Furthermore, the second battery connecting structure 500B, to whichcushioning members have been attached, is also stored in the secondhousing section 602 in such a way that a direction CP in which clearanceis positive is parallel to the bottom face 601U of the first housingsection 601, and a direction CM in which clearance is negative isperpendicular to the bottom face 602U of the second housing section 602.

Incidentally, the positive clearance means that a distance of an outersurface between cushioning members is 1.5 mm to 2 mm smaller than thesize of a housing section. The negative clearance means that a distanceof an outer surface between cushioning members is 3 mm to 4 mm largerthan the size of a housing section.

The first battery connecting structure 500A, to which cushioning membershave been attached, and the second battery connecting structure 500B, towhich cushioning members have been attached, are each connected to theprotective circuit board 700 with lead wires, which are substantiallythe same in length. Therefore, it is possible to shorten the wires, aswell as to make the impedance between the protective circuit board andone battery connecting structure equal to the impedance between theprotective circuit board and the other battery connecting structure.

As a result, when the two battery connecting structures are connected inparallel, it is possible to draw energy from batteries in an efficientmanner.

Moreover, a surface of the first battery connecting structure to behoused in the first housing section 601, on which the flat batteries areplaced is parallel to the bottom face 601U of the first housing section.Meanwhile, a surface of the second battery connecting structure on whichthe flat batteries are placed is perpendicular to the bottom face 602Uof the second housing section. Since the bottom face 601U of the firsthousing section and bottom face 602U of the second housing section areparallel to each other, the surface of the first battery connectingstructure, on which the flat batteries are placed is perpendicular tothe surface of the second battery connecting structure, on which theflat batteries are placed.

That is, when the battery pack is mounted on a bicycle, in the secondhousing section 602 that is positioned in a lower area, a surface of theshortest interval of an portion that is formed by a visible outline of abattery connecting structure and is substantially in the shape of arectangular parallelepiped, i.e. a surface that is at right angles to asurface of a battery connecting structure on which the flat batteriesare placed in the case of the diagram, is placed so as to run parallelto the bottom face of the second housing section 602.

On the bottom face of the first housing section 601, a surface a batteryconnecting structure, on which the flat batteries are placed is placedso as to be parallel to the bottom face. The surface of the firstbattery connecting structure, on which the flat batteries are placed andthe surface of the second battery connecting structure, on which theflat batteries are placed are disposed so as to cross each other atright angles. In this manner, the battery connecting structures, whichare the same in shape and structure, are mounted in the first thickhousing section 601 and in the second thin housing section 602.

In a process shown in FIG. 25, the first case body 600 is fixed to thesecond case body 660 with screws.

In the process, the second case body is placed on the first case body600. The second case body is fixed to the first case body 600 withscrews as the second case body is pushed in a direction in which theclearance of the battery connecting structure to which cushioningmembers have been attached is negative. As a result, the battery pack ofthe present invention is completed; in the battery pack, the batteryconnecting structure does not move even when vibrations or shocks areapplied.

FIG. 26 is a diagram illustrating an electric bicycle on which thebattery pack of the present invention is mounted.

An electric bicycle 1 has a frame 2 on which a battery pack 4 of thepresent invention is mounted. The battery pack 4 supplies power to adriving mechanism 3 of the electric bicycle.

As described above with reference to FIG. 24, the battery pack 4includes two housing sections that are different in structure butaccommodate the battery connecting structures that are the same inshape. A battery pack upper section 41, which is thick and correspondsto the first housing section 601 shown in FIG. 24, is positioned in aspace between a saddle 5 and a rear wheel. Therefore, the battery packupper section 41 does not come in contact with a leg or the like when arider rides the bicycle.

Moreover, a battery pack lower section 42, which is thin and correspondsto the second housing section 602[first→second] shown in FIG. 24, ispositioned in a space between a seat post 6 and the rear wheel. However,since the second hosing section, the battery connecting structure 500 isthin even, the second hosing section does not come in contact with apedal or leg even when a rider rotates the pedal 7.

The battery pack 4 of the present invention is mounted directly on theframe 2 that is subject to vibrations and shocks from a road surface. Inthe battery pack 4, measures have been taken against vibrations andshocks. Therefore, the battery pack 4 operates in a stable manner.

INDUSTRIAL APPLICABILITY

According to the battery pack of the present invention, energy-efficientlithium ion batteries or the like covered with the film casing materialare definitely protected from shocks and the like by the light weightbattery protective member. Moreover, a plurality of coating materialshaving different physical properties are applied to the protectivecircuit board inside the battery pack depending on the height of thecircuit component, so that it is possible to form a reliable protectivefilm on both the tall circuit components and short circuit components,thereby providing a battery pack provided with a high-reliableprotective circuit board not adversely affected by liquid.

EXPLANATION OF SYMBOLS

1: Electric bicycle

2: Frame

3: Driving mechanism

4: Battery pack

41: Battery pack upper section

42: Battery pack lower section

5: Saddle

6: Seat post

7: Pedal

100: Unit battery

110: Unit battery main unit

111: Upper end portion

112: Lower end portion

120: Positive-electrode pull-out tab

125: Tab member

127: Hole

130: Negative-electrode pull-out tab

137: Hole

200: Holder member

203: Pull-out tab guide rib

210: First surface

211: First row

212: Second row

213: Pull-out tab guidance section

214: Pull-out tab guidance concave section

215: Pull-out tab insertion hole

220: Pull-out tab guide projecting section

221: Top section

222: Tapered side

250: Second surface

255: Nut housing section

256: Nut

257: Pull-out tab connection bolt

260: Divider piece

263: Positioning projecting section

270: Screw hole

271: Board fixing screw

300: Board

314: Pull-out tab guidance notch section

315: Pull-out tab extraction hole

316: Pull-out tab/divider piece extraction hole

317: Divider piece extraction hole

320 a, 320 b, 320 c: Thin-film electrode section

321: Metallic positive terminal electrode washer

322: Metallic negative terminal electrode washer

325: Pull-out tab connection screw hole

328: Positioning hole

329: Board fixing screw hole

331, 332: Terminal member

340: Connector

400: Battery protective member

410: First plate section

420: Notch section

421: First notch section

422: Second notch section

423: Third notch section

440: Second plate section

450: Battery protective member block

460: Two-sided adhesive tape

500: Battery connecting structure

504: Fourth cushioning member (thick)

505: Fifth cushioning member (thin)

600: First case body

601: First housing section

601U: Bottom face

602: Second housing section

602U: Bottom face

603: Circuit housing section

611: Discharge terminal attachment concave section

612: Charge terminal attachment concave section

613: Discharge terminal

614: Charge terminal

621: First cushioning member

622: Second cushioning member

660: Second case body

661: First housing section

662: Second housing section

663: Third cushioning section

673: Circuit housing section

680: Upper compartment section

681, 682: Drain hole

700: Protective circuit board

1-8. (canceled)
 9. A battery pack comprising: a battery connectingstructure on which a plurality of flat batteries are placed; and aprotective circuit board that protects the flat batteries duringcharging and discharging of the flat batteries, film formation for theprotective circuit board being made using a plurality of film formingmaterials different in viscosity, wherein circuit components implementedon the protective circuit board include: a circuit component having ahighest height from the board and having a surface covered only with afirst hardening resin, and a circuit component having a surface coveredonly with a second hardening resin whose viscosity is lower than thoseof the first hardening resin.
 10. The battery pack according to claim 9,wherein the circuit components are covered with the first hardeningresin in viscosity of 20 to 90 Pa·s at 25° C. and the second hardeningresin in viscosity of 0.3 to 1.0 Pa·s at 25° C., respectively.
 11. Thebattery pack according to claim 9, wherein the battery connectingstructure includes a battery protective member having at least platesection and a second plate section which are integrally connected toboth edge portions of a width direction of the plate section and extendssubstantially in a direction perpendicular to both surfaces of the firstplate section, wherein the flat batteries are plate section wherein theflat batteries are placed on the first plate section.
 12. The batterypack according to claim 11, wherein a surface on which the flatbatteries are placed is formed on both surfaces of the first platesection.
 13. The battery pack according to claim 11, wherein aflat-plate surface of the flat battery is put on the first platesection.
 14. The battery pack according to claim 11, wherein the flatbatteries are film-covered batteries.
 15. An electric bicycle comprisingthe battery pack as claimed in claim 9.